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Q: Can You Seal Old Concrete
A: Yes! Old concrete can be sealed for the first time or resealed if it has been previously sealed with a concrete sealer. Before sealing old concrete you want to make sure you determine if the concrete has been previously sealed. If a previous sealer has been used you want to make sure it is removed by acid etching or grinding. If the previous sealer is compatible you may be able to reseal without removing the previous sealer. (Solvent based acrylic concrete sealers can be applied on top of previous solvent based acrylics).
Once a previous sealer has been removed you are then going to want to clean the concrete. You want to make sure all mold, mildew, efflorescence, rust, grease and oil are removed from the concrete before sealing as you do not want to seal these elements into the concrete. If you are applying an epoxy floor coating you are going to want to make sure you have good surface profile which can be achieved by acid etching or grinding the concrete.
Since old concrete may have developed cracks throughout the years, you are going to want to make sure all cracks are filled. SikaFlex provides great crack repair products available in different colors to match any concrete substrate. If the concrete has extreme damage from spalling or pitting you may want to think about using a concrete overlay to resurface the existing concrete and then preventatively seal. Concrete overlays are essentially thin layers of concrete that is mixed up and applied on top of an existing slab.
Once the concrete is properly prepared you can then go about sealing the concrete. When choosing a concrete sealer determine the type of protection you are looking for before choosing a product. If you are looking to seal a driveway from road salts, use a penetrating salt repellent sealer. If you are looking to seal a basement from moisture use a waterproofing concrete coating.
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